Liquid crystal display and manufacture therefore

ABSTRACT

An electrode width of intermediate connection wiring which connects terminal electrode and common electrode is made narrower than an electrode width of terminal electrode at forming an electrode pattern on one of substrates configuring a liquid crystal display device. This enables the prevention of detrimental effect of cutting and polishing the periphery of a liquid crystal cell onto the terminal electrode. A laser irradiation process required for removing the common electrode is eliminated, and thus manufacturing cost may be reduced.

FIELD OF THE INVENTION

The present invention relates to liquid crystal display devices andmethod of manufacturing the same.

BACKGROUND OF THE INVENTION

This application is a U.S. national phase application of PCTInternational application PCT/JP99/01510.

The manufacturing of liquid crystal display devices includes a series ofprocesses of configuring a liquid crystal cell using substrate 1 onwhich an electrode pattern as shown in FIGS. 6 and 8 is formed , cuttingand removing the periphery of this liquid crystal cell at cut position2, and polishing the cut section to smooth the rough surface.

Terminal electrode 3 is formed near the cut position of substrate 1 forconnecting to an external circuit. A reference numeral 6 in FIGS. 6 and8 shows a display electrode.

In case of an active matrix array substrate having a switching devicesuch as a thin film transistor inside a liquid crystal cell, commonelectrode pattern 4 for short-circuiting terminal electrode 3 isprovided on substrate 1 for preventing destruction of any switchingelements by static electricity generated during the manufacturingprocesses of an array substrate and liquid crystal cell. Commonelectrode pattern 4 is then removed after cutting the periphery ofliquid crystal cell.

Even in the case of a liquid crystal cell not possessing a switchingdevice, a common electrode pattern for short-circuiting the terminalelectrode is also provided in order to prevent degradation of analigning film by static electricity. The common electrode pattern isthen removed after cutting the periphery of the liquid crystal cell.

These electrodes are conventionally formed with an ITO (indium tin oxideor tin oxide solid solution). In this case, as shown in FIGS. 5(a) and6, common electrode pattern 4 is automatically removed when cutting thesubstrate by providing common electrode pattern 4 outside cut position2.

However, recent demands for larger displays require a lower resistanceelectrode. For example, the Japanese Patent Laid-open Publication No.H9-230806 proposes the use of an Ag metal electrode.

In addition, for increasing the brightness of a reflective liquidcrystal display device as a mobile display apparatus, provision of areflector inside the liquid crystal cell is proposed by forming a metalelectrode functioning both as a reflector and electrode on a bottomsubstrate. This configuration uses a signal polarizer or no polarizer.As for materials of the metal electrode, Al and Ag materials arereceiving attention because they have low wiring resistance and highreflectance (e.g., the Japanese Patent Laid-open Publication Nos.H7-134300 and H8-179252).

However, the use of the metal electrode as terminal electrode 3, inparticular Al and Ag materials which are not hard metals, mayshort-circuit the adjacent terminal electrodes at the cut section of thesubstrate during polishing due to the ductility of the terminalelectrode material, as shown by a reference numeral 7 in FIG. 5(b),where adjacent terminal electrodes are intended to be electricallyisolated as shown in FIG. 5(a), as a result of the cutting and polishingprocesses of the liquid crystal cell.

To avoid the above short-circuiting, common electrode pattern 4 isprovided inside cut position 2 of the substrate, as shown in FIG. 8, andan additional process of separating terminal electrodes by removingcommon electrode pattern 4 (an area equivalent to laser irradiationwidth L) by laser irradiation, as shown in FIG. 7, is required aftercutting the periphery of the liquid crystal cell.

The present invention aims to offer a liquid crystal display and amethod of manufacturing the same which eliminate an additional processsuch as laser irradiation even when an electrode pattern is formed usinga ductile metal material.

SUMMARY OF THE INVENTION

The liquid crystal display of the present invention comprises a firstsubstrate; a terminal electrode made of metal provided inside the firstsubstrate; an intermediate connection wiring made of metal whose one endis connected to the terminal electrode and the other end reaches to asubstrate end; a second substrate; and a liquid crystal layer interposedbetween the first and second substrates. The width of the intermediateconnection wiring at the end of the first substrate is set to benarrower than the electrode width of the terminal electrode.

A method of manufacturing the liquid crystal display of the presentinvention includes the steps of

forming two or more terminal electrodes made of metal on the firstsubstrate inside a cut position for cutting and removing the peripheryof the substrate at a later process;

forming the common electrode wiring outside the cut position;

forming the intermediate connection wiring made of metal for connectingeach terminal electrode to common electrode wiring, whose width isnarrower than that of the terminal electrodes at the cut position;

interposing liquid crystal between the first and second substrates; and

cutting and removing the periphery of the substrate at the cut positionof the first substrate.

The present invention thus provides a liquid crystal display which doesnot cause short-circuiting between adjacent terminal electrodes evenwhen the substrate end is polished after cutting the substrate on whichthe electrode pattern made of ductile metal is formed.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a plan view of a substrate in accordance with a preferredembodiment of the present invention.

FIG. 2 is a plan view around a terminal electrode of a substrate inaccordance with the preferred embodiment of the present invention.

FIG. 3 is a magnified view of a key part in FIG. 1.

FIG. 4 is a sectional view of a reflective liquid crystal display inaccordance with the preferred embodiment of the present invention.

FIGS. 5a and 5 b are plan views around the terminal electrode in aconventional manufacturing of an electrode substrate.

FIG. 6 is a plan view of an example of the conventional electrodesubstrate.

FIG. 7. is a plan view around the terminal electrode for illustrating aconventional method of manufacturing the electrode substrate.

FIG. 8 is a plan view of another example of the conventional electrodesubstrate.

DESCRIPTION OF THE PREFERRED EMBODIMENT

A preferred embodiment of the present invention is described below withreference to FIGS. 1 to 4.

In FIG. 1, display electrode 6, terminal electrode 3 a connected to thisdisplay electrode 6 and disposed inside cut position 2 of a substrate,common electrode 4 prepared for static electricity disposed outside cutposition 2, and intermediate connection wiring 3 b for connectingterminal electrode 3 a and common electrode 4, as shown in FIGS. 2 and3, are formed on substrate 1. A peripheral portion of the substrateoutside cut position 2 is cut and removed at a later process.

FIG. 2 is a magnified view around the terminal electrode. As shown inFIG. 2, line width A of intermediate connection wiring 3 b is set to benarrower than electrode width D of terminal electrode 3 a.

FIG. 4 shows a reflective liquid crystal display manufactured using asubstrate on which electrode wiring is formed as described above. InFIG. 4, a display electrode also functions as a reflective electrode.

Manufacturing of the reflective liquid crystal display of the presentinvention is detailed next in accordance with the preferred embodiment.

First Exemplary Embodiment

First, 500 Å of Ti layer 18 and 2000 Å of Al layer 17 are sequentiallylaminated on the surface of bottom substrate 16 by DC magnetronsputtering using a Ti target and Al alloy target. An electrode patternas shown in FIG. 2 is formed by these two layers to create a specularreflection type metal reflective electrode. A switching device such as aTFT is not formed on this substrate.

Then, a 5 wt % N-methyl-2-pyrolidinone solution of polyimide is printedon the surface of bottom substrate 16 where the above electrodes areformed and top substrate 11 where ITO transparent electrode 13 isformed. After curing the substrates at 200° C., aligning layer 12 isformed by rotational rubbing using a rayon cloth to achieve 250° twistedSTN mode liquid crystal display.

Thermosetting sealing resin 15 in which a 5.5 μm diameter glass fibermixed at 1.0 wt % is printed at the peripheral sealing area of topsubstrate 11, and 5.0 μm diameter resin beads are scattered on thebottom substrate 16 at a ratio of 200 particles/mm². Top substrate 11and bottom substrate 16 are then adhered, and sealing resin is cured at150° for completing the liquid crystal cell.

After cutting and removing the periphery of the bottom substrate of theliquid crystal cell at cut position 2 in FIG. 1, the cut section ispolished for smoothening. Liquid crystal 14 which is made of ester typenematic liquid crystal with refractive-index anisotropy Δn of 0.16 mixedwith a predetermined amount of chiral liquid crystal is vacuum filledinto the liquid crystal cell. The inlet is sealed with UV-curing resin,and cured by UV irradiation.

Scattering film 10 is then laminated on top substrate 11 of the liquidcrystal cell as formed above. Scattering film 10 used in the presentinvention is a forward scattering film (trade name: Lumisty by SumitomoChemical Co. Ltd.), and a film having 0° and 50° scattering directionsmeasured from the normal film direction are laminated onto top substrate11. Polymer film 9 made of polycarbonate resin is then adhered onto thisscattering film 10. Polymer film 9 consists of two polymer films havingdifferent delay phase axes. One polymer film on the liquid crystal cellside has 0.3 μm retardation, and its delay phase axis with respect tothe orientation of top substrate 11 is 90°. The other polymer film ontop has 0.5 μm retardation, and its delay phase axis with respect to theorientation of top substrate 11 is 45°. Then, a neutral gray polarizer 8(SQ-1852AP by Sumitomo Chemical Co. Ltd.) with antiglare (AG) treatmentis adhered on to polymer film 9 so as to match its absorption axis tothe delay phase axis of the polymer film on the liquid crystal cellside.

A driving circuit for the liquid crystal cell consists of printedcircuit board 23 on which electronic components are mounted and TAB tapecarrier on which LSI chip 22 is mounted is connected to terminalelectrode 17 of the liquid crystal cell using anisotropic conductiveadhesive 20.

An exposed part of the terminal electrode between the electrode wherethe tape carrier is connected and sealing resin 15 is covered withacrylic resin 19 (TF 1141 by Hitachi Chemical Industry).

The above configuration provides a reflective liquid crystal displaydevice for achromatic black display with low reflectance, achromaticwhite display with high reflectance, and achromatic color changes fromblack to white by simple matrix driving with the {fraction (1/240)} dutyratio.

The influence of cutting and polishing on line width A, interval B, andlength C in FIG. 2, and the degree of damage caused by roughness of thecut section are examined for the above reflective liquid crystaldisplay. In addition, short-circuiting of adjacent terminal electrodesdue to ductility of metal by polishing the cut section is examined.

Specimens with fixed electrode width D of 45 μm in FIG. 2, line width Aof 40 μm, 30 μm, 20 μm, or 10 μm; interval B of 30 μm, 40 μm, 50 μm, or60 μm; and length C remaining after cuts of 100 μm, 200 μm, 300 μm, or400 μm are prepared. The influence of cutting and polishing is examinedfor these specimens.

Results indicated that with respect to the length C, cutting andpolishing in the specimen when length C is 100 μm cause damage toterminal electrode 3 a because minute roughness at the substrate cut endpenetrates to about 100 μm, and the surface needs to be made smooth bypolishing to about 100 μm inside the substrate cut position. Specimenswith 200 μm, 300 μm, and 400 μm for length C do not show any damage toterminal electrode 3 a as a result of cutting and polishing.

Consequently, a configuration that avoids the damage up to terminalelectrode 3 a by cutting and polishing is achievable by setting thelength C to 200 μm or longer.

Elongation of the metal at the cut section of the substrate by polishingcauses short-circuiting between adjacent intermediate connection wiringsin specimens with 30 μm, 40 μm, 50 μm, and 60 μm for electrode intervalB when line width A is 40 μm or 30 μm. In case of specimen with linewidth A of 20 μm, the metal partially elongated at the cut section as aresult of polishing when the electrode interval B is 30 μm. However,this partial elongation does not cause short-circuiting between adjacentintermediate connection wirings. No elongation of metal orshort-circuiting between adjacent intermediate connection wirings occurat the cut section as a result of polishing in specimens with electrodeinterval B of 40 μm, 50 μm, or 60 μm. When electrode width A is 10 μm,no elongation of the metal or short-circuiting between adjacentintermediate connection wirings occur in specimens with electrodeinterval B of 30 μm, 40 μm, 50 μm, or 60 μm.

Consequently, a configuration that avoids short-circuiting betweenadjacent intermediate connection wirings due to elongation of metal atthe substrate cut section by polishing is achievable by setting the linewidth of the intermediate connection wiring at the substrate cut sectionto 20 μm or below. Even better results are achieved when electrodeinterval B between adjacent electrodes is 40 μm or wider at the liquidcell cut section.

The same results are obtained when Al alloy layer 17 is thickened to5000 Å.

The above embodiment refers to an example of a reflective liquid crystaldisplay device which has display electrodes made of a metal electrode.However, the above results are applicable as long as the terminalelectrode and intermediate connection wiring are made of the metalelectrode. Accordingly, the present invention is also applicable to atransmissive liquid crystal display device whose display electrode isconfigured with the ITO.

The preferred embodiment also employs a substrate on which a switchingdevice such as a TFT is not formed. However, the present invention isalso naturally applicable to a substrate on which the switching deviceis formed, such as an active matrix array substrate, as long as theterminal electrode and intermediate connection wiring are made of themetal electrode. Application of the present invention improves thedisplay quality.

The Al alloy used in the preferred embodiment is one of metals havingthe highest ductility, and thus cutting and polishing may be implementedmore safely with other metals. Thus, the present invention is alsoapplicable to a layer containing Ag or Ag alloys, for example, which arebeing increasingly used as reflective electrodes because of their highreflectance.

Electrode width D of the terminal electrode in the above description isset to 45 μm. However, the electrode width is not limited as long as thewidth required for connecting electronic components for driving liquidcrystal cells to the terminal electrode of liquid crystal cell isachieved.

The preferred embodiment shown in FIG. 4 uses a substrate with theconfiguration shown in FIG. 3 only for bottom substrate 16. It isapparent that only top substrate 11 may use the processed substrateshown in FIG. 3 configured with the metal electrode from the terminalelectrode to the substrate cut section. Or, both bottom substrate 16 andtop substrate 11 may have a configuration of the present invention inwhich the metal electrode is used for the terminal electrode andintermediate connection wiring, and these two substrates may be adheredfor creating the liquid crystal cell.

As described above, the present invention prevents any damage to theterminal electrode due to the outer roughness of the substrate cutsection even when the liquid crystal cell substrate is cut and polishedat the cut position, and eliminates short-circuiting between adjacentelectrodes caused by elongation of metal at the cut section due topolishing, by making the line width of the intermediate connectionwiring connecting the terminal electrode and common electrode narrowerthan that of the terminal electrode.

Industrial Applicability

The present invention provides a liquid crystal display device whicheliminates the occurrence of short-circuiting between adjacent terminalelectrodes even when the cut end of the substrate, on which theelectrode pattern made of a metallic material having high conductivityand ductility is formed, is polished.

Consequently, the laser irradiation process which is conventionallyrequired for removing the common electrode can be omitted, reducing themanufacturing cost of the liquid crystal display device and thuscontributing to increased use of low-power consuming reflective liquidcrystal display devices and large high definition liquid crystal displaydevices.

What is claimed is:
 1. A liquid crystal display comprising: a firstsubstrate; a terminal electrode made of metal, said terminal electrodebeing disposed on a surface inside said first substrate; an intermediateconnection wiring made of metal, one end of said intermediate connectionwiring being connected to said terminal electrode and the other end ofsaid intermediate connection wiring reaching an end of said firstsubstrate; a second substrate; and a liquid crystal layer interposedbetween said first substrate and said second substrate; wherein a linewidth of said intermediate connection wiring at the end of said firstsubstrate is set to be narrower than an electrode width of said terminalelectrode, and wherein the line width of said intermediate connectionwiring at the end of said first substrate is set to be not greater than20 μm, and an interval between said adjacent intermediate connectionwirings is set to be not less than 40 μm.
 2. A liquid crystal displaycomprising: a first substrate; a terminal electrode made of metal, saidterminal electrode being disposed on a surface inside said firstsubstrate; an intermediate connection wiring made of metal, one end ofsaid intermediate connection wiring being connected to said terminalelectrode and the other end of said intermediate connection wiringreaching an end of said first substrate; a second substrate; and aliquid crystal layer interposed between said first substrate and saidsecond substrate; wherein a line width of said intermediate connectionwiring at the end of said first substrate is set to be narrower than anelectrode width of said terminal electrode wherein said terminalelectrode and said intermediate connection wiring are at least asingle-layer film containing one of Al, Al alloy, Ag, and Ag alloywherein the line width of said intermediate connection wiring at the endof said first substrate is set to be not greater than 20 μm, and aninterval between said adjacent intermediate connection wirings is set tobe not less than 40 μm.
 3. A liquid crystal display comprising: a firstsubstrate; a terminal electrode made of metal, said terminal electrodebeing disposed on a surface inside said first substrate; an intermediateconnection wiring made of metal, one end of said intermediate connectionwiring being connected to said terminal electrode and the other end ofsaid intermediate connection wiring reaching an end of said firstsubstrate; a second substrate; and a liquid crystal layer interposedbetween said first substrate and said second substrate; wherein a linewidth of said intermediate connection wiring at the end of said firstsubstrate is set to be narrower than an electrode width of said terminalelectrode wherein said intermediate connection wiring is formed for notless than 200 μm from the end of said first substrate to inside the saidfirst substrate wherein the line width of said intermediate connectionwiring at the end of said first substrate is set to be not greater than20 μm, and an interval between adjacent intermediate connection wiringsis set to be not less than 40 μm.
 4. A liquid crystal displaycomprising: a first substrate; a terminal electrode made of metal, saidterminal electrode being disposed on a surface inside said firstsubstrate; an intermediate connection wiring made of metal, one end ofsaid intermediate connection wiring being connected to said terminalelectrode and the other end of said intermediate connection wiringreaching an end of said first substrate; a second substrate; and aliquid crystal layer interposed between said first substrate and saidsecond substrate; wherein a line width of said intermediate connectionwiring at the end of said first substrate is set to be narrower than anelectrode width of said terminal electrode wherein said terminalelectrode and said intermediate connection wiring are at least asingle-layer film containing one of Al, Al alloy, Ag, and Ag alloywherein said intermediate connection wiring is formed for not less than200 μm from the end of said first substrate to inside said firstsubstrate, and wherein the line width of said intermediate connectionwiring at the end of said first substrate is set to be not greater than20 μm, and an interval between said adjacent intermediate connectionwirings is set to be not less than 40 μm.
 5. A method for manufacturinga liquid crystal display comprising: forming a plurality of displayelectrodes and a plurality of terminal electrodes made of metal on afirst substrate inside a cut position for cutting and removing aperiphery of said first substrate at a later process; forming commonelectrode wiring outside said cut position; forming an intermediateconnection wiring made of metal connecting each of said terminalelectrodes and said common electrode wiring, said intermediateconnection wiring having a line width narrower than a width of saidterminal electrodes; interposing liquid crystal between a secondsubstrate and said first substrate; and cutting and removing saidperiphery of said first substrate at said cut position, wherein the linewidth of said intermediate connection wiring at said cut position is setto be not greater than 20 μm, and an interval between said adjacentintermediate connection wirings is set to be not less than 40 μm.
 6. Amethod for manufacturing a liquid crystal display comprising: forming aplurality of display electrodes and a plurality of terminal electrodesmade of metal on a first substrate inside a cut position for cutting andremoving a periphery of said first substrate at a later process; formingcommon electrode wiring outside said cut position; forming anintermediate connection wiring made of metal connecting each of saidterminal electrodes and said common electrode wiring, said intermediateconnection wiring having a line width narrower than a width of saidterminal electrodes; interposing liquid crystal between a secondsubstrate and said first substrate; and cutting and removing saidperiphery of said first substrate at said cut position wherein saidterminal electrode and said intermediate connection wiring are at leasta single-layer containing one of Al, Al alloy, Ag, and Ag alloy, andwherein the line width of said intermediate connection wiring at saidcut position is set to be not greater than 20 μm, and an intervalbetween said adjacent intermediate connection wirings is set to be notless than 40 μm.
 7. A method for manufacturing a liquid crystal displaycomprising: forming a plurality of display electrodes and a plurality ofterminal electrodes made of metal on a first substrate inside a cutposition for cutting and removing a periphery of said first substrate ata later process; forming common electrode wiring outside said cutposition; forming an intermediate connection wiring made of metalconnecting each of said terminal electrodes and said common electrodewiring, said intermediate connection wiring having a line width narrowerthan a width of said terminal electrodes; interposing liquid crystalbetween a second substrate and said first substrate; and cutting andremoving said periphery of said first substrate at said cut positionwherein said intermediate connection wiring is formed inward for notless than 200 μm from said cut position, and wherein the line width ofsaid intermediate connection wiring at said cut position is set to benot greater than 20 μm, and an interval between said adjacentintermediate connection wirings is set to be not less than 40 μm.
 8. Amethod for manufacturing a liquid crystal display comprising: forming aplurality of display electrodes and a plurality of terminal electrodesmade of metal on a first substrate inside a cut position for cutting andremoving a periphery of said first substrate at a later process; formingcommon electrode wiring outside said cut position; forming anintermediate connection wiring made of metal connecting each of saidterminal electrodes and said common electrode wiring, said intermediateconnection wiring having a line width narrower than a width of saidterminal electrodes; interposing liquid crystal between a secondsubstrate and said first substrate; and cutting and removing saidperiphery of said first substrate at said cut position wherein saidterminal electrode and said intermediate connection wiring are at leasta single-layer containing one of Al, Al alloy, Ag, and Ag alloy whereinsaid intermediate connection wiring is formed inward for not less than200 μm from said cut position, and wherein the line width of saidintermediate connection wiring at said cut position is set to be notgreater than 20 μm, and an interval between said adjacent intermediateconnection wirings is set to be not less than 40 μm.
 9. A liquid crystaldisplay according to claim 1, wherein at least one of said first andsecond substrates is an active matrix substrate.
 10. A liquid crystaldisplay according to claim 2, wherein at least one of said first andsecond substrates is an active matrix substrate.
 11. A liquid crystaldisplay according to claim 3, wherein at least one of said first andsecond substrates is an active matrix substrate.
 12. A liquid crystaldisplay according to claim 4, wherein at least one of said first andsecond substrates is an active matrix substrate.
 13. A liquid crystaldisplay according to claim 5, wherein at least one of said first andsecond substrates is an active matrix substrate.
 14. A liquid crystaldisplay according to claim 6, wherein at least one of said first andsecond substrates is an active matrix substrate.
 15. A liquid crystaldisplay according to claim 7, wherein at least one of said first andsecond substrates is an active matrix substrate.
 16. A liquid crystaldisplay according to claim 8, wherein at least one of said first andsecond substrates is an active matrix substrate.